Recipe

Make Batter

1. Preheat oven to 350°F. Line two 9-inch circular cake pans with parchment paper and set aside.
2. Sift flour and cocoa onto piece of parchment paper and set aside.
3. Place egg whites in bowl of stand mixer fitted with whisk attachment and beat on high until foamy. Add cream of tartar and beat on medium until soft peaks form. With mixer still running, gradually add 1⁄4 cup sugar and continue beating until stiff, glossy peaks form. Transfer egg whites to large mixing bowl.
4. Return bowl of mixer to stand, still fitted with whisk attachment. Add egg yolks, remaining 1 1⁄2 cups sugar and vanilla. Beat on high speed until yolks are very pale yellow and have doubled in volume, 3 to 5 minutes. Gently fold egg yolks into stiff egg whites, then fold in flour and cocoa until no streaks remain.

Bake Cakes

1. Divide batter evenly between prepared cake pans and, using small offset spatula, spread evenly. Bake for 20 to 22 minutes, until cakes spring back in centre when lightly touched.
2. Remove from oven. Allow cakes to cool in pans for about 15 minutes. Run knife around edge of cake pans to loosen cakes and turn out onto wire rack, peel off parchment and allow to cool completely.

Make Whipped Cream

1. In stand mixer fitted with whisk attachment, whip cream, sugar and vanilla on high speed until soft peaks form. Store, covered, in refrigerator for up to 2 days.

Make Chocolate Sauce

1. In small saucepan over medium-high heat, whisk together water, sugar and cocoa until sugar has dissolved and mixture has reached a low boil. Remove from heat, add chocolate chips and whisk until fully combined and melted.

Assemble Cake

1. Turn cakes top-side up and place one on serving plate. Spread generous scoop of whipped cream across cake and sprinkle with half of the mixed berries. Top with remaining cake and repeat. Refrigerate until ready to serve.
2. Before serving, gently warm chocolate sauce in pan over low heat, or heat for about a minute in microwave (be careful not to overheat — you want it just warm, not so hot it melts the whipped cream). Drizzle sauce over top of cake and allow to drip down sides. Store in refrigerator for up to 3 days.